The U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA) published this Floodplain Assessment (FA) for the Los Alamos Mainline Make Piggable Pipeline Project at Los Alamos National Laboratory.
Office of NEPA Policy and Compliance
July 16, 2026
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Floodplain Assessment for the Los Alamos Mainline Make Piggable Pipeline Project at Los Alamos National Laboratory; Santa Fe and Los Alamos Counties, New Mexico
The New Mexico Gas Company (NMGC) proposes to install new pipe segments through excavation along a 12-inch Main Line (Los Alamos ML) natural gas pipeline in Santa Fe and Los Alamos Counties, New Mexico. The proposed pipeline runs along Los Alamos County, Department of Energy (DOE), tribal and U.S. Forest Service-managed and private property. Work would occur within existing and new right-of-way (ROW) along New Mexico Highway 502 (NM 502). Two locations for proposed excavation and replacement of the line are within floodplain areas in Los Alamos Canyon and Pueblo Canyon along NM 502 with a projected total area of disturbance to be 3.38 acres within the floodplain.
The proposed project would result in negligible direct and indirect impacts to the Los Alamos Canyon and the Pueblo Canyon floodplains. Temporary disturbances with the floodplains would cease following completion of construction activities. Best management practices would be implemented. This proposed project would not modify flow paths within the floodplains from pre-project to post-project conditions. No effects on lives and property associated with floodplain modifications are anticipated.
The 15-day public comment period ends on August 3, 2026. Please provide comments on this Floodplain Assessment to Karen Armijo:
- Email: Karen.Armijo@nnsa.doe.gov
- Mail: U.S. Department of Energy
- Los Alamos Field Office
- Attn: Karen Armijo
- 3747 West Jemez Road
- Los Alamos, NM 87544
After the close of the public comment period and prior to issuing a floodplain statement of findings, DOE/NNSA will reevaluate the practicability of alternatives to the proposed floodplain action, mitigating measures, and take into account all substantive comments received during the public comment period. DOE/NNSA will endeavor to allow 15 days of public review prior to implementation of the proposed action.